Improve `opt_expr` performance #265

Job	Run time
pre_job	4s
pre_docs_job	6s
Reusable build (ubuntu-latest)	11m 15s
Reusable build (macos-latest)	6m 12s
Run docs tests (ubuntu-latest)	30s
Run tests (ubuntu-latest)	16m 7s
Run tests (macos-latest)	12m 5s
	46m 19s

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